The invention relates to portable x-ray based bone densitometry systems and methods and techniques useful at least in such systems and methods.
X-rays or gamma-rays can be used to measure the density and distribution of bone in the human body in order to help health professionals assess and evaluate projected bone mineral density, which in turn can be used to monitor age-related bone loss that can be associated with diseases such as osteoporosis.
In bone densitometry, a patient typically is placed on a table such that the patient's spine extends along the length of the table, along a direction that can be called the Y-axis in Cartesian coordinates. For a supine patient, the left and right sides are in a direction typically called the X-axis. A source at one side of the patient transmits radiation through the patient to a radiation detector at the other side. The source and the detector typically are mechanically linked by a structure such as a C-arm to ensure their alignment along a source-detector axis which is transverse (typically perpendicular) to the Y-axis. The detector in a fan beam-type system typically is an elongated array of detector elements arranged along a line or an arc. By means of mechanically moving the C-arm and/or moving the table, a region of interest in a patient on the table can be scanned with the radiation.
Typical regions of analysis in bone densitometry include the spine, hip, forearm, and wrist, scanned individually. They can be covered individually within a reasonable time by a fan beam that has a relatively narrow angle in a single pass or, alternatively, by a pencil beam scanning a raster pattern. Another analysis region is termed "oblique hip" in which the hip is viewed at an angle relative to the horizontal and vertical directions. Another analysis region is referred to as "whole body" in which the entire patient body is scanned and analyzed for bone density and possibly also for "body composition" or the percentages of fat and muscle in the body.
X-ray bone densitometry systems have been made by the owner of this application under the tradenames QDR-2000+, QDR-2000, QDR-1500, QDR-1000plus, and QDR-1000. The following commonly owned U.S. patents pertain to such systems and are hereby incorporated by reference herein: U.S. Pat. Nos. 4,811,373, 4,947,414, 4,953,189, 5,040,199, 5,044,002; 5,054,048, 5,067,144, 5,070,519, 5,132,995 and 5,148,455; and 4,986,273 and 5,165,410 (each assigned on its face to Medical & Scientific Enterprises, Inc. but now commonly owned). Other bone densitometry systems are believed to have been made by the Lunar Corporation of Madison, Wis. (see, e.g., the system which is believed to be offered under the tradename Expert and U.S. Pat. Nos. 5,228,068, 5,287,546 and 5,305,368, none of which is admitted to be prior art against this invention). It is believed that other manufacturers also have offered bone densitometry products.
It would be advantageous, in many instances, to have an X-ray bone densitometry system for the measurement of bone density, that is easily transportable with a minimum of setup. Ideally, the system apparatus would be capable of going through standard doorways with no disassembly. In the United States of America, doorways for medical buildings typically are 36 inches (0.91 meters) wide.
While portable shadowgraph-type x-ray radiography systems, which can be transported through standard doorways, are available for hospitals, nursing homes, medical clinics and physician medical offices, portable densitometry systems have not been available to the medical community. Part of the reason has no doubt been that the C-arm structures and motorized patient tables used in known bone densitometry systems are bulky and have required relatively large floor footprints and clearance in order for those systems to achieve their full range of scanning motions.
It is an object of the present invention to create a portable bone densitometry system having an examination table unit, which in fully assembled, but in partially collapsed form can be passed through a doorway having a width of 36 inches (0.91 m).
It is another object of the present invention to create a portable bone densitometry system which is fully self-contained, i.e., does not require disassembly or reassembly before passing through doors and which does not require component re-alignment after transportation.
It is also an object of the present invention to create a system of x-ray bone densitometers, with each unit comprising the system having different scanning motion capabilities from purely Y-axis-only scanning motion along at least part of the length of a patient on the patient table, to complete X-, Y- and Z-axis scanning motions, including rotation of the C-arm source-detector support about a rotational axis which is parallel to the Y-axis of the patient table.
The portable bone densitometry system of the present invention achieves the aforementioned objects of small linear dimensions for passage through doorways, self containment and minimum setup time in order to become operational at multiple locations.
The portable x-ray bone densitometry system of the present invention is suitable for transportation between rooms of a medical facility through generally standard doorways. The system has a base portion capable of rolling ambulation by at least one human operator during transportation and selective stabilization on a floor for patient scanning. The apparatus has a patient table extending parallel to a Y-axis of an XYZ coordinate system for supporting a patient at a patient position. The patient table includes a central portion coupled with the base portion, and at least one table leaf coupled with the table central portion, for extending table length parallel to the Y-axis. The apparatus also has a source-detector support coupled with the base portion; an x-ray source, coupled with the source-detector support, for emitting a beam of x-rays to irradiate at any one time a scan line which is transverse to the Y-axis; and an x-ray detector, coupled with the source-detector support arm in alignment with the source at opposite sides of the patient table along a source-detector axis which is transverse to the Y-axis, for receiving x-rays from the source after passage thereof through the patient position. A scanning mechanism moves at least one of the patient table and the source-detector support relative to the other to scan the patient position with the x-ray beam. The patient table may have a pair of leaves attached to the central portion with hinges at opposite ends thereof.